U.S. patent number 5,171,808 [Application Number 07/803,120] was granted by the patent office on 1992-12-15 for cross-linked anionic and amphoteric polymeric microparticles.
This patent grant is currently assigned to American Cyanamid Company. Invention is credited to Elieth W. Harris, Dan S. Honig, Roger E. Neff, Roderick G. Ryles.
United States Patent |
5,171,808 |
Ryles , et al. |
December 15, 1992 |
Cross-linked anionic and amphoteric polymeric microparticles
Abstract
Novel compositions comprising anionic and/or amphoteric organic
polymeric microparticles are disclosed, along with a method for
their production. The products are useful in flocculating a wide
variety of dispersions of suspended solids and in paper-making.
Inventors: |
Ryles; Roderick G. (Milford,
CT), Honig; Dan S. (New Canaan, CT), Harris; Elieth
W. (Bridgeport, CT), Neff; Roger E. (Stamford, CT) |
Assignee: |
American Cyanamid Company
(Stamford, CT)
|
Family
ID: |
27064885 |
Appl.
No.: |
07/803,120 |
Filed: |
July 22, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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535626 |
Jun 11, 1990 |
|
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Current U.S.
Class: |
526/264; 525/107;
525/193; 526/207; 526/213; 526/303.1; 526/317.1 |
Current CPC
Class: |
C08F
2/32 (20130101); D21H 17/375 (20130101); D21H
17/43 (20130101); D21H 21/54 (20130101) |
Current International
Class: |
C08F
2/32 (20060101); D21H 17/00 (20060101); D21H
17/43 (20060101); D21H 21/00 (20060101); D21H
21/54 (20060101); D21H 17/37 (20060101); C08F
026/10 (); C08F 020/56 (); C08F 020/06 (); C08F
002/24 (); C08F 008/00 () |
Field of
Search: |
;526/264 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Susan Budavari, Maryadele J. O'Neil, Ann Smith, and Patricia E.
Heckelman, The Merck Index, pp. 21, 935 and 1572, 1989..
|
Primary Examiner: Schofer; Joseph L.
Assistant Examiner: Cheng; Wu C.
Attorney, Agent or Firm: Van Riet; Frank M.
Parent Case Text
This is a continuation of co-pending application Ser. No.
07/535,626, filed Jun. 11, 1990 now abandoned.
Claims
We claim:
1. A composition comprising cross-linked anionic or amphoteric
polymeric microparticles derived solely from the polymerization of
an aqueous solution of at least of one monomer, said microparticles
having an unswollen number average particle size diameter of less
than about 0.75 micron, a solution viscosity of at least about 1.1
mPa.s, a cross-linking agent content of about 4 molar parts to
about 4000 parts per million, based on the monomeric units present
in the polymer, and an ionicity of at least about 5 mole
percent.
2. A composition as defined in claim 1 wherein said crosslinking
agent content is from about 20 to about 4,000 molar parts per
million.
3. A composition as defined in claim 1 wherein said crosslinking
agent content is from about 50 to about 2,000 molar parts per
million.
4. A composition as defined in claim 1 wherein said crosslinking
agent is a difunctional monomer selected from
N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide,
polyethyleneglycol dimethacrylate, polyethyeneglycol diacrylate,
N-vinyl acrylamide, glycidyl acrylate, divinylbenzene, acrolein,
glyoxal, diepoxy compounds, epichlorohydrin and mixtures of the
foregoing.
5. A composition as defined in claim 4 wherein said crosslinking
agent comprises N,N'-methylenebisacrylamide.
6. A composition as defined in claim 1 wherein said said unswollen
diameter is less than 0.5 micron.
7. A composition as defined in claim 1 wherein the organic polymer
microparticle is composed of at least one ethylenically unsaturated
non-ionic monomer.
8. A composition as defined in claim 1 wherein the organic polymer
microparticle is composed of at least one anionic monomer selected
from acrylic acid, methylacrylic acid, ethylacrylic acid,
2-acrylamido-2-methylpropanesulfonic acid or mixtures or salts
thereof.
9. A composition as defined in claim 8 wherein said anionic monomer
comprises sodium acrylate, sodium methylacrylate, sodium
ethylacrylate or sodium 2-acrylamido-2-methylpropanesulfonate.
10. A composition as defined in claim 1 wherein the organic polymer
microparticle is amphoteric and is composed of from 1% to 99% of an
anionic monomer selected from acrylic acid, methacrylic acid,
ethacrylic acid, 2-acrylamido-2-methylpropane sulfonic acid or
salts thereof and from 99% to 1% of a cationic monomer selected
from acryloxyethyltrimethylammonium chloride,
3-methyacrylamidopropyltrimethylammonium chloride,
diallydimethylammonium chloride and mixtures thereof.
11. A composition as defined in claim 7 wherein said non-ionic
ethylenically unsaturated monomer is selected from acrylamide;
methacrylamide; N,N-dialkylacrylamides: N-alkylacrylamides;
N-vinylmethacetamide; N-vinyl methylformamide; N-vinyl pyrrolidone
and mixtures thereof.
12. A composition as defined in claim 1 wherein said organic
polymer microbead is composed of sodium acrylate and
acrylamide.
13. A process for the preparation of a composition as defined in
claim 1, said process comprising:
(a) admixing
(i) an aqueous solution comprising at least one ethylenically
unsaturated anionic monomer alone or in admixture with a cationic
monomer, and at least one crosslinking agent and, optionally, at
least one ethylenically unsaturated non-ionic monomer;
(ii) an oily phase comprising at least one hydrocarbon liquid;
(iii) an effective amount of surfactant or surfactant mixture, so
as to form an inverse emulsion; and
(b) subjecting the inverse emulsion obtained in step (a) to
polymerization conditions.
14. A process as defined in claim 13 wherein said monomer solution
of step (a)(i) comprises sodium acrylate as said anionic monomer,
N,N-methylenebisacrylamide as said crosslinking agent and
acrylamide as said non-ionic monomer.
15. A process as defined in claim 13 wherein said oily phase of
step (a)(ii) comprises a saturated hydrocarbon.
16. A process as defined in claim 13 wherein said surfactant or
surfactant mixture of step (a)(iii) comprises polyoxythylene
sorbitol hexaoleate or a mixture thereof with sorbitan
sesquioleate.
17. A process as defined in claim 13 wherein said polymerization
conditions of step (b) comprise adding a polymerization
initiator.
18. A process as defined in claim 17 wherein said polymerization
initiator comprises sodium metabisulfite or tertiary-butyl
hydroperoxide.
19. A process as defined in claim 13 wherein said polymerization
conditions of step (b) comprise subjecting said inverse emulsion to
ultraviolet irradiation.
20. A process as defined in claim 13 wherein said aqueous solution
of step (a)(i) additionally contains an effective amount of a
chain-transfer agent selected from an alcohol, mercaptan,
phosphite, sulfite, or a mixture thereof.
21. A process as defined in claim 13 which also includes step (c),
comprising recovering the composition from the emulsion.
Description
The present invention relates to structured anionic and amphoteric
polymeric microparticles and a method for their preparation.
BACKGROUND OF THE INVENTION
Cross-linked anionic and amphoteric, organic polymeric compositions
are known to those skilled in the art and are useful in a variety
of solid-liquid separation applications, particularly in the
flocculation of various dispersions of suspended solids, such as
sewage sludge, and in the thickening of cellulosic paper pulp
suspensions. Modern concerns about environmental pollution and the
increasing cost of materials have made it highly desirable to
produce flocculating agents which cause higher degrees of
separation at lower dosage levels.
EP 0,202,780 describes the preparation of polymeric, crosslinked,
cationic acrylamide polymer beads by conventional inverse emulsion
polymerization techniques. Crosslinking is accomplished by the
incorporation of a difunctional monomer, such as
methylenebisacrylamide, into the polymer. This crosslinking
technology is well known in the art. The patentee teaches that the
crosslinked beads are useful as flocculants.
Typically, the particle size of polymers prepared by conventional
inverse water-in-oil emulsion polymerization processes are limited
to a range of about 1-5 microns, since no particular advantage in
reducing the particle size has hitherto been apparent. The precise
particle size which is achievable in inverse emulsions is
determined by the concentration and activity of the surfactant(s)
employed and these are customarily chosen on the basis of emulsion
stability and economic factors.
Leong, et al., in Inverse Microemulsion Polymerization, J. of Phys.
Chem., Vol. 86, No. 23, Jun. 24, 1982, pp 2271-3, discloses
polymerization of acrylamide in an inverse microemulsion. The
author, also discloses having prepared crosslinked polyacrylamide
latices or microgels by using a 100:1 mixture of
acrylamide-methylenebisacrylamide. No anionic or amphoteric
monomers are mentioned or is their use as a flocculating agent or
paper-making additive.
EPO 0173605 teaches the production of microbeads having a diameter
ranging from about 49-87 nm and produced from terpolymers of vinyl
acetate (84.6), ethyl acrylate (65.4) and acrylic acid (4.5) or
methacrylonitrile (85), butyl acrylate (65) and acrylic acid (3).
These polymeric beads are disclosed as added to an LBKP pulp slurry
in order to evaluate the resultant paper for sizing degree, paper
force enhancement and disintegratability. These polymer beads fall
outside the scope of those claimed in the present invention in that
the ionic content thereof is too small to impart any appreciable
improvement during usage.
Additionally, U.S. Pat. No. 4,681,912 discloses the production of
microparticles of acrylamide and acrylic acid, for example,
utilizing a microemulsion process. The patent, however, fails to
teach the cross-linking of the particles so as to render them
water-insoluble or their use in paper-making.
SUMMARY OF THE INVENTION
According to the present invention, there are provided compositions
comprising crosslinked, anionic and/or amphoteric, organic,
polymeric, microparticles, having an unswollen number average
particle size diameter of less than about 0.75 micron, preferably
less than about 0.5 micron, a solution viscosity of at least 1.1,
preferably from about 1.1 to about 2.0, mPa.s, a crosslinking agent
content of above about 4 molar parts per million, based on the
monomeric units present in the polymer, and an ionicity of at least
about 5%.
The preferred anionic monomers for use in the practice of the
present invention comprises acrylic acid, methacrylic acid,
ethacrylic acid, 2-acrylamido-2-alkylsulfonic acids where the alkyl
group contains 1 to 6 carbon atoms, such as
2-acrylamido-2-propane-sulfonic acid or mixtures of any of the
foregoing and their alkaline salts. Especially preferred are the
sodium salts of acrylic acid, methacrylic acid, and
2-acrylamido-2-methylpropane sulfonic acid.
The preferred amphoteric polymers for the use in the practice of
the present invention comprise copolymers of one or more of the
foregoing anionic monomers and one or more of the following
cationic ethylenically unsaturated monomers selected from, from
example, acryloxyethyltrimethylammonium chloride;
diallydimethylammonium chloride;
3-(meth)acrylamidopropyltrimethylammonium chloride;
3-acrylamidopropyltrimethylammonium-2-hydroxypropylacrylate
methosulfate; trimethylammoniumethyl methacrylate methosulfate;
1-trimethylammonium-2-hydroxypropylmethacrylate methosulfate;
methacryloxyethyltrimethylammonium chloride; or mixtures of any of
the foregoing.
The preferred ethylenically unsaturated non-ionic monomers for use
in the practice of the present invention are selected from
acrylamide; methacrylamide; N,N-dialkylacrylamides;
N-alkylacrylamides; N-vinylmethacetamide; N-vinyl methylformamide;
N-vinyl pyrrolidone and mixtures thereof. Especially preferred is
acrylamide.
The preferred compositions encompassed by the present invention are
1) anionic monomers alone or 2) a mixture of anionic and cationic
monomers, each copolymerized with the ethylenically unsaturated
non-ionic monomers disclosed above. Especially preferred is
acrylamide copolymerized with sodium acrylate.
Also, according to the present invention, there is provided a
process for the preparation of compositions as defined above, the
process comprising:
(a) admixing
(i) an aqueous solution comprising at least one ethylenically
unsaturated anionic monomer alone or in admixture with a cationic
monomer and at least one crosslinking agent and, optionally, at
least one ethylenically unsaturated non-ionic monomer;
(ii) an oily phase comprising at least one hydrocarbon liquid;
and
(iii) an effective amount of surfactant or surfactant mixture, so
as to form an inverse emulsion which, when subjected to
polymerization conditions, results in a polymer having a particle
size of less than about 0.75 micron in unswollen diameter; and
(b) subjecting the inverse emulsion obtained in step (a) to
polymerization conditions.
A preferred feature of the present invention, comprises a process
employing an aqueous solution comprising sodium acrylate as the
anionic monomer, N,N-methylenebisacrylamide as the crosslinking
agent and acrylamide as the non-ionic monomer; an oily phase
comprising a saturated hydrocarbon; and an effective amount of a
surfactant mixture comprising polyoxyethylene (20) sorbitan
monooleate and polyoxyethylene sorbitol hexaoleate, sufficient to
produce particles of less than about 0.75 micron in unswollen
number average particle size diameter.
Polymerization of the inverse emulsion may be carried out by adding
a polymerization initiator, such as sodium metabisulfite or
tert-butyl hydroperoxide, or by subjecting the inverse emulsion to
ultraviolet irradiation. Also contemplated by the present invention
is adding an effective amount of chain-transfer agent to the
aqueous solution of the inverse emulsion, such as an alcohol,
mercaptan, phosphite, sulfite or mixture of any of the foregoing.
The process of the present invention may also comprise a step for
recovering the composition from the inverse emulsion.
The resultant organic polymeric particles are useful in a method of
making paper from an aqueous suspension of cellulose fibers,
whereby the drainage properties of the suspension are improved by
including in the suspension 0.1 to 20 lbs/ton, based on the dry
weight of paper furnish solids, of the anionic or amphoteric
cross-linked organic polymer microbead having an unswollen number
average particle size diameter of less than about 0.75 micron, a
solution viscosity of at least about 1.1, preferably about 1.1 to
about 2.0 mPa.s, a cross-linking agent content of above about 4
molar parts per million, based on the monomeric units present in
the polymer, and at least 5% ionicity, preferably in the presence
of a molecular weight Ser. No. 07/536,382 filed Jun. 11, 1990, now
abandoned and refiled as Ser. No. 07/540,667, filed Jun. 18, 1990
as a continuation-in-part.
DETAILED DESCRIPTION OF THE INVENTION
Cross-linked, anionic or amphoteric, organic polymeric microbeads
having an unswollen number average particle size diameter of less
than about 0.75 micron, a solution viscosity of from about 1.1 to
about 1.5 mPa.s, a crosslinking agent content of above about 4
molar parts per million, based on the monomeric units present in
the polymer, and an ionicity of at least about 5 mole percent, are
generally formed by the polymerization of at least 5% of an
ethylenically unsaturated anionic monomer and, for amphoteric
microparticles, at least about 5% of one cationic monomer, and,
optionally at least one non-ionic comonomer in the presence of a
crosslinking agent in a water-in-oil inverse emulsion employing an
effective amount of surfactant or surfactant mixture to produce
microbeads of less than about 0.75 micron.
The amphoteric polymers for the use in the practice of the present
invention comprise copolymers of one or more of the foregoing
anionic monomers and one or more of the following cationic
ethylenically unsaturated monomers (meth)acrylates of
dialkylaminoalkyl compounds, and salts and quaternaries thereof and
in particular monomers of N,N-dialkylaminoalkyl(meth)acrylamides,
and salts and quaternaries thereof, such as
N,N-dimethylaminoethyacrylamides; and the acid or quaternary salts
thereof and the like. Cationic monomers which may be used herein
are of the following general formulae: ##STR1## where R.sub.1 is
hydrogen or methyl, R.sub.2 is hydrogen or lower alkyl of 1-4
carbon atoms, R.sub.3 and/or R.sub.4 are hydrogen, alkyl of 1-12
carbon atoms, aryl, or hydroxyethyl and R.sub.2 and R.sub.3, or
R.sub.3 and R.sub.4, can combine to form a cyclic ring containing
one or more hetero atoms, and Z is the conjugate base of an acid; X
is oxygen or --NR.sub.1, wherein R.sub.1 is as defined above, and A
is an alkylene group of 1-12 carbon atoms, or ##STR2## where
R.sub.5 and R.sub.6 are hydrogen or methyl, R.sub.7 is hydrogen or
alkyl of 1-12 carbon atoms, and R.sub.8 is hydrogen, alkyl of 1-12
carbon atoms, benzyl or hydroxyethyl; and Z is as defined
above.
These ethylenically unsaturated anionic, cationic and non-ionic
monomers may be copolymerized to produce anionic and amphoteric
copolymers. Preferably, acrylamide is copolymerized with a anionic
monomer. Anionic copolymers useful in the practice of this
invention comprise from about 0 to about 95 parts, by weight of
non-ionic monomer and about 5 to about 100 parts, by weight, of
anionic monomer, based on the total polymer weight. Amphoteric
polymers may be produced from about 1-99 parts, by weight, same
basis, of anionic monomer and from about 99-1 parts, by weight, of
cationic monomer, optionally with from about 0-75 parts, by weight,
of a non-ionic monomer, the total weight of the anionic monomer and
cationic monomer being at least 5%. Polymerization of the monomers
is conducted in the presence of a polyfunctional crosslinking agent
to form the crosslinked composition. The polyfunctional
crosslinking agent comprises molecules having either at least two
double bonds, a double bond and a reactive group, or two reactive
groups. Illustrative of those containing at least two double bonds
are N,N-methylenebisacrylamide, N,N-methylenebismethacrylamide,
polyethyleneglycol diacrylate, polyethyleneglycol dimethacrylate,
N-vinyl acrylamide, divinylbenzene, triallylammonium salts,
N-methylallylacrylamide and the like. Polyfunctional branching
agents containing at least one double bond and at least one
reactive group include, glycidyl acrylate, acrolein,
methylolacrylamide and the like. Polyfunctional branching agents
containing at least two reactive groups include aldehydes such as
glyoxal, diepoxy compounds, epichlorohydrin and the like.
Crosslinking agents are to be used in sufficient quantities to
assure a crosslinked composition. Preferably at least about 4 molar
parts per million of crosslinking agent, based on the monomeric
units present, are employed to induce sufficient crosslinking and
preferred is a crosslinking agent content of from about 4 to about
6000 molar parts per million, more preferably about 20-4000 and
most preferably about 50-2000 molar parts per million.
One method of obtaining the polymeric microparticles of this
invention is to polymerize the monomers in a microemulsion.
Polymerization in microemulsions and inverse microemulsions is
known to those skilled in this art. P. Speiser reported in 1976 and
1977 a process for making spherical "nanoparticles" with diameters
less than 800A by (1) solubilization of polymerizable molecules,
e.g. acrylamide and methylenebisacrylamide and other materials, e.g
drugs, in micelles and (2) polymerizing the monomers in the
micelles. J. Pharm. Sa., 65(12), 1763 (1976) and U.S. Pat. No.
4,021,364. Both inverse water-in-oil and oil-in-water
"nanoparticles" were prepared by this process. While not
specifically called microemulsion polymerization by the author,
this process does contain all the features which are currently used
to define microemulsion polymerization. These reports also
constitute the first examples of polymerization or acrylamide in a
microemulsion. Since then, numerous publications reporting
polymerization of hydrophobic polymers in the oil phase of
microemulsions have appeared. See, for example, Stoffer and Bone,
J. Dispersion Sci. and Tech., 1(1), 37, 1980 and Atik and Thomas,
J. Am. Chem. Soc'y, 103(14), 4279 (1981); and GB 2161492A.
The ionic and amphoteric microemulsion polymerization process may
be conducted by (i) preparing a monomer microemulsion by adding an
aqueous solution of the monomers to a hydrocarbon liquid containing
appropriate surfactant or surfactant mixture to form an inverse
monomer microemulsion consisting of small aqueous droplets which,
when polymerized, result in polymer particles of less than 0.75
micron in size, dispersed in the continuous oil phase and (ii)
subjecting the monomer microemulsion to free radical
polymerization.
In order to obtain an inverse microemulsion, it is generally
necessary to use particular conditions whose main parameters are as
follows: surfactant concentration, HLB of surfactant or surfactant
mixture, temperature, nature of the organic phase and composition
of the aqueous phase.
The aqueous phase comprises an aqueous mixture of the monomers,
anionic or a mixture of anionic and cationic and optionally
non-ionic, and the crosslinking agent, as defined above. The
aqueous monomer mixture may also comprise such conventional
additives as are desired. For example, the mixture may contain
chelating agents to remove polymerization inhibitors, pH adjusters,
initiators and other conventional additives.
Essential to the formation of the microemulsion, which may be
defined as a swollen, transparent and thermodynamically stable
micelle solution without agitation, comprising two liquids
insoluble in each other and a surfactant, in which the micelles are
much smaller than in an emulsion, is the selection of appropriate
organic phase and surfactant.
The selection of the organic phase has a substantial effect on the
minimum surfactant concentration necessary to obtain the inverse
microemulsion. This organic phase may comprise of a hydrocarbon or
hydrocarbon mixture. Saturated hydrocarbons or mixtures thereof are
the most suitable in order to obtain inexpensive formulations
(lower surfactant content) of inverse microemulsions. Typically,
the organic phase will comprise benzene, toluene, fuel oil,
kerosene, odorless mineral spirits and mixtures of any of the
foregoing.
The ratio by weight of the amounts of aqueous and hydrocarbon
phases is chosen as high as possible, so as to obtain, after
polymerization, a microemulsion of high polymer content.
Practically, this ratio may range, for example from about 0.5 to
about 3:1, and usually is about 2:1.
The one or more surfactants are selected in order to obtain an HLB
(Hydrophilic Lipophilic Balance) value ranging from about 8 to
about 11. In addition to the appropriate HLB value, the
concentration of surfactant must also be optimized, i.e. sufficient
to form an inverse emulsion having the correct particle size.
Typical surfactants useful in the practice of this invention, in
addition to those specifically discussed above, may be anionic,
cationic or non-ionic and are selected from polyoxyethylene (20)
sorbitan trioleate, sorbitan trioleate, sodium
di-2-ethylhexylsulfosuccinate, oleamidopropyldimethylamine; sodium
isostearyl-2-lactate and the like.
Polymerization of the emulsion may be carried out in any manner
known to those skilled in the art. Initiation may be effected with
a variety of thermal and redox free-radical initiators including
azo compounds, such as azobisisobutyronitrile; peroxides, such as
t-butyl peroxide; organic compounds, such as potassium persulfate
and redox couples, such as ferrous ammonium sulfate/ammonium
persulfate. Polymerization may also be effected by photochemical
irradiation processes, irradiation, or by ionizing radiation with a
60 Co source. Preparation of an aqueous product from the emulsion
may be effected by inversion by adding it to water which may
contain a breaker surfactant. Optionally, the polymer may be
recovered from the emulsion by stripping or by adding the emulsion
to a solvent which precipitates the polymer, e.g. isopropanol,
filtering off the resultant solids, drying and redispersing in
water.
The product of this invention is useful in facilitating a wide
range of solid-liquid separation operations. The products of this
invention may be used to dewater biologically treated suspensions,
such as sewage and other municipal or industrial sludges; the
drainage of cellulosic suspension, such as those found in paper
production, e.g. paper waste; and the settling and dewatering of
various inorganic suspensions, e.g. refinery waste, coal waste,
etc.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following examples illustrate the present invention. They are
not be construed as limitations on the present invention except as
set forth in the appended claims.
EXAMPLES 1-5
Procedure for the Preparation of Anionic Microemulsion
The master batch of aqueous phase is made by mixing acrylic acid
(AA), as the sodium salt, 200 parts deionized water, 56.5% sodium
hydroxide, crystal acrylamide (AMD), 0.3 part 10% pentasodium
diethylenetriaminepentaacetate, 39.0 parts additional deionized
water, and 1.5 parts of 0.518% copper sulfate pentahydrate
together. To 110.2 parts of this aqueous phase solution, 6.5 parts
deionized water, 0.25 part 1% t-butyl hydroperoxide and
N,N-methylene bisacrylamide (MBA) are added. This aqueous phase is
mixed with an oil phase containing 77.8 parts of low odor paraffin
oil, 3.6 parts sorbitan sesquioleate and 21.4 parts polyoxyethylene
sorbitol hexaoleate.
This emulsion is deaerated with nitrogen for 20 minutes. The
polymerization is then initiated with gaseous SO.sub.2. The
polymerization is then allowed to exotherm to 40.degree. C. and is
controlled at 40.degree. C. (+5.degree. C.) with ice water. The ice
water is removed when cooling is no longer required. The nitrogen
is continued for one hours. The total polymerization time is 2.5
hours.
If desired, the polymer may be recovered from the emulsion by
stripping or by adding the emulsion to a solvent which precipitates
the polymer, e.g. isopropanol, filtering off the resultant solids,
drying and redispersing in water.
At the time of use e.g. as a paper-making additive, the recovered
polymer may be dispersed in water. The emulsion, microbeads may
also be directly dispersed in water. Depending on the surfactant
and levels used in the emulsion dispersion may require using high a
hydrophilic lipophilic balance (HLB) inverting surfactant such as
an ethoxylated alcohol; polyoxyethyllated sorbitol hexaoleate;
diethanolamine oleate; ethoxylated laurel sulfate etc. as in known
in the art.
The procedure for preparing amphoteric emulsions e.g. 15AA/60AMD/25
dimethylaminoethylacrylate (DMEA)/349 ppm MBA, is repeated for the
preparation of the anionic emulsions with the exception that the
concentration of the individual monomers employed are adjusted
accordingly.
Various monomers are polymerized in accordance with the above
procedure. The results are set forth in Table I, below.
TABLE I ______________________________________ Preparation of
Anionic Microbeads Copolymer Composi- tions (Mole %) MBA PS SV
Example AMD AA NaAPS PPM NM mPa .multidot. S
______________________________________ 1 70 30 -- 349 130 1.19 2 40
60 -- 1381 120 1.10 3 0 100 -- 1985 80 1.35 4 70 -- 30 995 -- 1.37
5 70 -- 30 10,086 -- 1.15 6 70 30 -- 1000 464 -- 7 70 30 -- 1000
149 1.02 8 70 30 -- 1000 106 1.06
______________________________________ NaAPS = Sodium
2Acrylamido-2-methylpropane Sulfonic Acid PS = Number Average
Particle Size in Nanometers SV = Solution Viscosity (0.1% polymer
in M NaCl, 25.degree. C. using a Brookfield UL adapter at 60
rpm
EXAMPLE 9
In paper making processes it is found that the addition of anionic
microbeads, preferably with a high molecular weight cationic
polymer to a conventional paper making stock increases the drainage
rate of water from the paper. The following examples illustrate
this utility but are not to be construed to limit the invention in
any manner whatsoever.
A 70/30 hardwood/softwood bleached kraft pulp is used containing
25% CaCO.sub.3 for alkaline papermaking at a pH of 8.0 Drainage is
a measure of the time required for a certain volume of water to
drain through the paper and is here measured as a10X drainage. (K.
Britt, TAPPI 63(4) p67 (1980). Hand sheet are prepared on a Noble
and Wood sheet machine. In the test examples, the linear cationic
copolymer is a 10 mole % of acryloxyethyltrimethylammonium chloride
(AETMAC) and 90 mole % of acrylamide (AMD) of 5,000,000 to
10,000,000 mol. wt. with a charge density of 1.2 meg./g. and SV-4.0
cps. The anionic microbeads in Table II are added separately to the
thin paper stock. The cationic polymer is added to the test furnish
in a "Vaned Britt Jar" and subjected to 800 rpm stirring for 30
seconds. The anionic microbead is then added and subjected to 800
rpm stirring for 30 seconds and then drainage times are measured.
The results of testing are set forth in Table II, below.
TABLE II ______________________________________ Drainage Aid Test
Data Anionic Drain- Ex- Polymer Dosage age am- Cationic Dosage
Microbead of (lb/ Time ple Polymer (lb/ton) Example No. ton) (Sec)
______________________________________ 6 0- -- 161.1 7 10 AETMAC/ 2
116.9 90 AMD 8 10 AETMAC/ 2 1- (0.5) 75.8 90 AMD 9 10 AETMAC/ 2 1-
(1.0) 72.1 90 AMD 10 10 AETMAC/ 2 1- (2.0) 84.3 90 AMD 11 10
AETMAC/ 2 2- (0.5) 66.3 90 AMD 12 10 AETMAC/ 2 2- (1.0) 72.4 90 AMD
13 10 AETMAC/ 2 2- (2.0) 74.7 90 AMD 14 10 AETMAC/ 2 3- (0.5) 78.8
90 AMD 15 10 AETMAC/ 2 3- (1.0) 74.1 90 AMD 16 10 AETMAC/ 2 3-
(2.0) 80.2 90 AMD 17 10 AETMAC/ 2 4- (0.5) 95.0 90 AMD 18 10
AETMAC/ 2 4- (1.0) 86.6 90 AMD 19 10 AETMAC/ 2 4- (2.0) 95.5 90 AMD
20 10 AETMAC/ 2 5- (0.5) 119.7 90 AMD 21 10 AETMAC/ 2 5- (1.0)
121.8 90 AMD 22 10 AETMAC/ 2 5- (2.0) 111.4 90 AMD
______________________________________
The drainage time for the untreated alkaline paper stock is 161.1
seconds. Addition of the linear, cationic polymer, 10 AETMAC/90
AMD, at a level of 2 lbs/ton decreases the drainage time to 116.9.
Further decreases in drainage time are obtained by the joint
addition of the anionic microbeads of this invention of doses of
0,5, 1.0 and 2.0 lbs/ton with the 2 lbs/ton of the cationic
polymer. The microbead 70 AMD/30 Na AMPS/10,086 ppm MBA has little
effect on drainage due to the excessively high degree of
cross-linking and is outside the scope of this invention. The
higher degree anionicity of 2 microbeads (40 AMD/60 AA/1381 ppm
MBA-120nm and 100AA/1985 ppm MBA-80 nm) improves drainage time over
those of the lower degree of anionicity microbeads 70 AMD/30
NaAPS/995 ppm MBA. The 1.0 lb/ton dosage of anionic microbead gives
better drainage times than either the 0.5 or 2.0 lbs/ton dosage.
The only exception is with the microbead 40AMD/60 AA/1,381 ppm MBA
where the 0.5 lb/ton dosage is the most desirable.
EXAMPLES 23-27
Anionic microbeads of 5 and 10 mole percent of anionic charge and
amphoteric microbeads with a 5 mole % higher anionic charge than
cationic charge are made by the procedure of Example 1 and are
shown in Table III. The microbeads have a particle size under 0.5
micron in Examples 23-27.
TABLE III
__________________________________________________________________________
Preparation of Anionic and Amphoteric Microbeads Copolymer
Compositions (Mole %) MBA Example AMD NaAc NaAPS DMEA ppm PS NM SV
mPa .multidot. S
__________________________________________________________________________
23 90 10 -- -- 496 -- 1.34 24 95 5 -- -- 97 -- 1.89 25 85 -- 10 5
1026 -- 1.40 26 55 -- 25 20 5101 -- 1.59 27 60 -- -- 40 100 100 --
__________________________________________________________________________
DMEA = Acryloxylethyltrimethylammonium Chloride See Table I for
other legends
EXAMPLE 28
The anionic and amphoteric microbeads of Table III are used in the
paper making process described in Example 2. The results are
substantially the same.
EXAMPLES 29-33
The procedure of Example 1 is again followed except that different
monomers are employed in the preparation of the microbead. The
results are set forth in Table IV, below.
TABLE IV ______________________________________ Non-Ionic Anionic
Monomer Monomer MBA Example (%) (%) PPM
______________________________________ 29 AM-50 MMA-50 117 30 AM-65
VSA-35 226 31 AM-75 DADM-25 198 32 -- NaAPS-100 316 33 MAM-90 AA-10
441 ______________________________________ MAM = methacrylamide MMA
= methacrylic acid VSA = vinylsulfonic acid DADM =
diallydimethylammonium chloride
The above mentioned patents and publications are incorporated
herein by reference.
Many variations of the present invention will suggest themselves to
those skilled in this art in light of the above detailed
description. Chain-transfer agents may be optionally added to the
monomer solution. Also contemplated are all methods of
polymerization and dewatering processes.
All such obvious modifications are within the full intended scope
of the appended claims.
* * * * *